CAIRO (AP) -- A bombing on a main Cairo road leading to the Giza pyramids killed six police and wounded another three on Friday, the deadliest attack on security forces in the capital in more than six months.

The bombing, near a mosque on a wide avenue often used by tour buses, hit a police checkpoint, smashing several cars and blowing the windows out of police SUVs. Gravel, debris, and leaves littered the ground, as investigators inspected the area and masked troops stood guard with automatic weapons.

"We heard the blast and rushed to the scene and found police vehicles damaged," said Abdel Hamid Abdulla, who was nearby. "We saw some police were injured, and some of their legs had been cut off," he said.

State-run news agency MENA said the blast targeted security forces but did not elaborate on what caused the explosion. A security official said that two bombs placed in the area exploded during a security patrol. The official spoke on condition of anonymity because he was not authorized to brief journalists.

A shadowy group called Hasm, or "Decisiveness," which the government suspects is linked to the now-banned Muslim Brotherhood, claimed responsibility for the attack. It has claimed previous attacks in Cairo, including a shooting against the country's former chief Muslim theologian and a car bomb against the chief prosecutor's deputy. Both escaped unhurt.

"There is no safety or security for you as long as we hold our weapons in jihad for God, there is either victory or martyrdom," the group said in a statement posted online.

Insurgents have carried out a number of attacks in Egypt since the 2013 military ouster of an elected Islamist president. The violence has been concentrated in the northern Sinai Peninsula, where Islamic State-linked militants are battling the army.

Friday's attack was the deadliest in Cairo since May, when gunmen opened fire on a microbus filled with plainclothes police in the suburb of Helwan, killing eight of them. IS claimed the attack.

Most of the attacks in Cairo have been small-scale bombings, including one in October that targeted a police convoy and killed a pedestrian bystander.

Friday's attack comes as President Abdel-Fattah el-Sissi is defending tough economic measures undertaken by his government to address a growing financial crisis and secure a $12 billion loan from the International Monetary Fund.

The government floated the Egyptian pound last month and slashed fuel subsidies, steps that were welcomed by the IMF and the business community but caused a spike the price of many goods, worsening the economic plight of ordinary Egyptians.

The austerity measures could fuel a backlash against el-Sissi, who rose to power after leading the military ouster of President Mohammed Morsi three years ago. Morsi had been freely elected a year earlier, but his rule proved divisive and the military stepped in amid massive protests demanding his resignation.